The present invention relates generally to electric vehicles (EVs), and more specifically, but not exclusively, to intentionally inefficient operation (e.g., excess power dissipation) of a drive inverter/electric motor for generation of excess heat used to enhance vehicle performance at reduced ambient temperature.
EV designers continue to find ways to improve efficiencies in propulsion and energy conversion between a propulsion battery and a propulsion electric motor. Heat is a principle way that inefficiencies appear, and in many parts of the EV design, designers include cooling systems and other design elements that are designed to maintain the battery at a safe operating temperature and otherwise reduce and mitigate high temperatures. Typically fluidic cooling systems, heat exchangers, and coolant paths are designed to isolate the battery from “standard” adverse affects of heating the battery. U.S. patent application Ser. No. 12/835,486 entitled “THERMAL MANAGEMENT SYSTEM WITH DUAL MODE COOLANT LOOPS” filed 13 Jul. 2010 is hereby expressly incorporated herein by reference for all purposes.
There are many ways to provide torque control for the electric motor of an EV. A preferred implementation of a torque control using modulation of a flux linkage (flux) is described in U.S. Pat. No. 7,847,501 entitled “VARYING FLUX VERSUS TORQUE FOR MAXIMUM EFFICIENCY” filed 7 Mar. 2008 which is hereby expressly incorporated herein by reference for all purposes. That patent describes flux control to increase efficiency or decrease the power loss of the EV throughout its operating range.
Cold weather operation of an EV poses additional design challenges as battery performance has a generally inverse relationship to temperature. What is needed is an apparatus and method for mitigating cold ambient performance degradation of the EV.